Cable tools are used to drill wells by a dropping action. The cable tool is attached to a cable, lowered into a well hole and repetitively raised and dropped. A cutting face on the lower end of the cable tool cuts, chisels and crushes rock and earth during the repetitive dropping action. Often, the bottom of the well hole is filled with water, so that the cable tool operates in a water environment.
With continued cable tool drilling, the well hole bottom accumulates rock and earth particles that have been cut and crushed by the cable tool. This accumulation of rock and earth particles impairs the drilling ability of the cable tool. Eventually, the cable tool must be removed from the well hole and a cleanout tool is lowered into the well hole to remove the accumulated debris. Cable tools have been designed to simultaneously pump debris from the bottom of the well hole as the cable tool cuts in the dropping action, such as disclosed in a patent to L. Garrison, U.S. Pat. No. 1,399,108, wherein the lifting cable is operable to activate a pump within the cable tool as well as to repetitively lift and drop the cable tool. Such conventional cable tool designs have been found to be generally expensive and impractical from an engineering and economic standpoint.
A long-felt need persists for an improved, relatively inexpensive, cable tool capable of removing debris from the bottom of a well hole during drilling operations. By removing such debris, the improved cable tool may continue to drill for an extended drilling period relative to conventional cable tools before the improved cable tool must be removed for cleanout of the well hole. Moreover, removal of debris from the bottom of the hole improves the efficiency of the cable tool bit, significantly increasing the rate of penetration.